Effects of nitrogen levels and irrigation regimes on assimilate translocation of barley cultivars in semi-arid climate of Fars province

Barley is commonly grown in dryland conditions of Iran, where drought stress during grain filling stage can limit productivity and increase the dependency on reserved assimilate. A field experiment was conducted to investigate the effects of irrigation regimes and Nitrogen (N) levels on assimilate translocation of two barley cultivars (Yousefsix-rowed and Nimrouztwo-rowed) in 2011 and 2012 at Fars Agricultural Research Center using split-split-plot design. There were three levels of water regimes (full-irrigation (I100), 75% and 50% of I100:I75 and I50, respectively) in 2011. Rainfed treatment (I0) was included in 2012. Three N levels (0, 60 and 120 kg ha−1) were used. Grain yield was positively affected by N fertilizer application and negatively by water stress during the grain filling period. The reduction of grain yield by water stress was intensified by increasing N supply. Also, severe deficit irrigation (I0) declined remobilization and reserved assimilate contribution to grain by 54.1% and 8.7% in 0 kg N ha-1crops and by 74.7% and 43.7% in 120 kg N ha-1 crops, respectively, as compared to well watered plots. Two-rowed cultivar significantly showed higher assimilate remobilization and grain yield than six-rowed cultivar under I50 and I0; by contrast, six-rowed cultivar had similar or higher performances in terms of these traits under I100 and I75. This study showed that optimizing irrigation and N rates and selection of the suitable cultivars in semi-arid Mediterranean climate of Fars province can increase assimilate remobilization and consequently grain yield.